This invention is an improvement upon the apparatus taught and illustrated in U.S. Pat. No. 4,871,182 to Altherr et al., which disclosure is incorporated herein by reference. Further, this application refers to and is an improvement on an invention taught in U.S. Pat. No. 5,176,396 to Hawthorne et al. for a fifth wheel unlocking device with fluid power redundancy.
Fifth wheel devices include a plate which supports the forward bed of a trailer. A kingpin is generally affixed to the trailer bed and extends into a center opening of the fifth wheel plate. Fifth wheels have included a pivotally connected jaw to engage and hold the kingpin against horizontal and vertical withdrawal. Generally the jaw closes and locks on the kingpin as the tractor and trailer are brought together. However, there is a mechanism provided to unlock the jaw to permit horizontal release of the kingpin and to allow for separation of the tractor and trailer, that is when the trailer is stationary and the tractor is thereafter powered forward. The mechanism is generally operable by the tractor driver and includes safeguards to avoid accidental release.
There have been earlier designs for automatically unlatching fifth wheels, for example the device shown and illustrated in U.S. Pat. No. 2,471,854 to Bies et al. However, experience with over the road hauling during the last several decades has developed an abundance of caution against automatically operated fifth wheels and, largely for reasons of safety, the tractor-trailer industry has generally disdained power-released mechanisms for tractor-trailer separation. Thus modern over the road fifth wheels, such as that shown in U.S. Pat. No. 4,871,182 to Altherr et al., have incorporated locking features, which are solely manually operable from the exterior of the tractor cab. These locking/unlocking features and devices have previously not been regarded as suitable for powered operation. However, as trucks have tended to become larger in size and incorporated aerodynamic design features, it has become more difficult for the operator to reach, grasp and operate the actuating mechanism for the fifth-wheel lock, and the problem is exaggerated and exacerbated for persons of smaller stature. Further, even taller individuals have difficulty with manual operation of the fifth-wheel disengaging apparatus without soiling and tearing clothing, and they may sustain physical impairments, such as back sprains and the like.